Inter-anchored multilayer refractory coatings

ABSTRACT

In one aspect, articles are described herein comprising refractory coatings employing an inter-anchored multilayer architecture. Articles having refractory coatings described herein, in some embodiments, are suitable for high wear and/or abrasion applications such as metal cutting operations. A coated article described herein comprises a substrate and a coating deposited by CVD adhered to the substrate, the coating including a refractory layer comprising a plurality of sublayer groups, a sublayer group comprising a Group IVB metal nitride sublayer and an adjacent layer alumina sublayer, the Group IVB metal nitride sublayer comprising a plurality of nodules interfacing with the alumina sublayer.

RELATED APPLICATION DATA

The present application is a continuation application pursuant to 35U.S.C. § 120 of U.S. patent application Ser. No. 14/563,692 filed Dec.8, 2014.

FIELD

The present invention relates to refractory coatings and, in particular,to refractory coatings deposited by chemical vapor deposition (CVD) forcutting tool applications.

BACKGROUND

Cutting tools, including cemented carbide cutting tools, have been usedin both coated and uncoated conditions for machining various metals andalloys. In order to increase cutting tool wear resistance, performanceand lifetime, one or more layers of refractory material have beenapplied to cutting tool surfaces. TiC, TiCN, TiN and/or Al₂O₃, forexample, have been applied to cemented carbide substrates by CVD and byphysical vapor deposition (PVD). While effective in inhibiting wear andextending tool lifetime in a variety of applications, refractorycoatings based on single or multi-layer constructions of the foregoingrefractory materials have increasingly reached their performance limits,thereby calling for the development of new coating architectures forcutting tools.

SUMMARY

In one aspect, articles are described herein comprising refractorycoatings employing an inter-anchored multilayer architecture. Briefly, acoated article described herein comprises a substrate and a coatingdeposited by CVD adhered to the substrate, the coating including arefractory layer comprising a plurality of sublayer groups, a sublayergroup comprising a Group IVB metal nitride sublayer and an adjacentlayer alumina sublayer, the Group IVB metal nitride sublayer comprisinga plurality of nodules interfacing with the alumina sublayer. In someembodiments, the Group IVB metal nitride sublayer and the adjacentalumina sublayer of a sublayer group are nanolayers. Moreover, thecoating can also comprise one or more inner layers between therefractory layer and the substrate. Further, the coating can compriseone or more outer layers over the refractory layer.

These and other embodiments are described further in the detaileddescription which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a cutting tool substrate according to one embodimentdescribed herein.

FIG. 2 illustrates a schematic cross-section of a coated cutting toolaccording to one embodiment described herein.

FIG. 3 is a cross-sectional scanning electron microscopy (SEM) image ofa refractory layer according to one embodiment described herein.

FIG. 4 is a SEM image of a section of the refractory layer provided inFIG. 3.

FIG. 5(a) is a plan view SEM image of an alumina sublayer surface of asublayer group according to one embodiment described herein, and FIG.5(b) is a plan view SEM image of a prior CVD alumina surface.

DETAILED DESCRIPTION

Embodiments described herein can be understood more readily by referenceto the following detailed description and examples and their previousand following descriptions. Elements, apparatus and methods describedherein, however, are not limited to the specific embodiments presentedin the detailed description and examples. It should be recognized thatthese embodiments are merely illustrative of the principles of thepresent invention. Numerous modifications and adaptations will bereadily apparent to those of skill in the art without departing from thespirit and scope of the invention.

In one aspect, articles are described herein comprising refractorycoatings employing an inter-anchored multilayer architecture. Articleshaving refractory coatings described herein, in some embodiments, aresuitable for high wear and/or abrasion applications such as metalcutting operations. A coated article described herein comprises asubstrate and a coating deposited by CVD adhered to the substrate, thecoating including a refractory layer comprising a plurality of sublayergroups, a sublayer group comprising a Group IVB metal nitride sublayerand an adjacent layer alumina sublayer, the Group IVB metal nitridesublayer comprising a plurality of nodules interfacing with the aluminasublayer. In some embodiments, the Group IVB metal nitride sublayer andthe adjacent alumina sublayer of a sublayer group are nanolayers.Moreover, the coating can also comprise one or more inner layers betweenthe refractory layer and the substrate. Further, the coating cancomprise one or more outer layers over the refractory layer.

Turning now to specific components, coated articles described hereincomprise a substrate. A coated article can comprise any substrate notinconsistent with the objectives of the present invention. For example,a substrate can be a cutting tool or tooling used in wear applications.Cutting tools include, but are not limited to, indexable cuttinginserts, end mills or drills. Indexable cutting inserts can have anydesired ANSI standard geometry for milling or turning applications.Substrates of coated articles described herein can be formed of cementedcarbide, carbide, ceramic, cermet or steel. A cemented carbidesubstrate, in some embodiments, comprises tungsten carbide (WC). WC canbe present in a cutting tool substrate in an amount of at least about 80weight percent or in an amount of at least about 85 weight percent.Additionally, metallic binder of cemented carbide can comprise cobalt orcobalt alloy. Cobalt, for example, can be present in a cemented carbidesubstrate in an amount ranging from 1 weight percent to 15 weightpercent. In some embodiments, cobalt is present in a cemented carbidesubstrate in an amount ranging from 5-12 weight percent or from 6-10weight percent. Further, a cemented carbide substrate may exhibit a zoneof binder enrichment beginning at and extending inwardly from thesurface of the substrate.

Cemented carbide substrates can also comprise one or more additives suchas, for example, one or more of the following elements and/or theircompounds: titanium, niobium, vanadium, tantalum, chromium, zirconiumand/or hafnium. In some embodiments, titanium, niobium, vanadium,tantalum, chromium, zirconium and/or hafnium form solid solutioncarbides with WC of the substrate. In such embodiments, the substratecan comprise one or more solid solution carbides in an amount rangingfrom 0.1-5 weight percent. Additionally, a cemented carbide substratecan comprise nitrogen.

A cutting tool substrate can comprise one or more cutting edges formedat the juncture of a rake face and flank face(s) of the substrate. FIG.1 illustrates a cutting insert substrate according to one embodimentdescribed herein. As illustrated in FIG. 1, the substrate (10) hascutting edges (12) formed at junctions of the substrate rake face (14)and flank faces (16). The substrate (10) also comprises an aperture (18)for securing the substrate (10) to a tool holder.

As described herein, a coating adhered to the substrate includes arefractory layer deposited by CVD comprising a plurality of sublayergroups, a sublayer group comprising a Group IVB metal nitride sublayerand an adjacent alumina sublayer, the Group IVB metal nitride sublayercomprising a plurality of nodules interfacing with the alumina sublayer.Sublayer groups of the refractory layer can be adjacent to another orspaced apart from one another by intervening layer(s) in the refractorylayer. Further, any desired number of sublayer groups can form therefractory layer. For example, a refractory layer can comprise 4 to 100sublayer groups.

FIG. 2 illustrates a schematic of a coated cutting tool according to oneembodiment wherein the refractory layer is deposited on an inner layerof the coating. The coated cutting tool (20) of FIG. 2 comprises acutting tool substrate (21) and a coating (22) adhered to the substrate(21). The coating (22) comprises a refractory layer (23) having aplurality of sublayer groups (24). For ease of illustration in FIG. 2,the refractory layer (23) is formed of four sublayer groups (24), eachsublayer group (24) comprising an alumina sublayer (25) and a Group IVBmetal nitride sublayer (26), the Group IVB metal nitride sublayer (26)having nodules for interfacing with the alumina sublayer (25). Anynumber of sublayer groups (24) can be employed in the refractory layer(23) depending on desired thickness of the refractory layer (23) and/orother performance factors. An inner layer (27) of the coating ispositioned between the refractory layer (23) and the cutting toolsubstrate (21). As described further herein, the inner layer (27) can bea single layer or multiple layers.

Individual sublayer groups can exhibit various constructions along thethickness of the refractory layer. Generally, the Group IVB metalnitride sublayer of a sublayer group is a nanolayer having a thicknessless than 100 nm. The Group IVB metal nitride sublayer, for example, canhave a thickness selected from Table I.

TABLE I Group IVB Metal Nitride Sublayer Thickness ≤100 nm  ≤50 nm  3nm-100 nm  5 nm-80 nm 10 nm-70 nmImportantly, the Group IV metal nitride sublayer comprises a pluralityof nodules for interfacing with the adjacent alumina sublayer of thesublayer group. The nodules can exhibit a generally spherical shape,elliptical shape or irregular shape. In some embodiments, nodule shapevaries within a single Group IVB metal nitride sublayer. Additionally,nodule shape can vary across Group IVB metal nitride sublayers ofindependent sublayer groups. Nodules of a Group IVB metal nitridesublayer can generally have sizes less than 1 μm. In some embodiments,nodules have a size selected from Table II.

TABLE II Nodule Size of Group IVB Metal Nitride Sublayer 20 nm-500 nm 50nm-500 nm 75 nm-350 nm 100 nm-400 nm  100 nm-200 nm  25 nm-300 nmFurther, the nodules can be dispersed over surfaces of the Group IVBmetal nitride sublayer. Moreover, the nodules can be present on one orboth sides of the Group IVB metal nitride sublayer of a sublayer group.When present on both sides of the Group IVB metal nitride sublayer, thenodules can interface with alumina sublayers of adjacent sublayergroups. Nodules of the Group IVB metal nitride sublayer can assist inanchoring the laminated structure formed by the multiple sublayergroups, leading to performance enhancements of the refractory layer.FIG. 3 is a cross-sectional back-scattering SEM image taken at amagnification of 20,000× of a refractory layer formed according to theCVD parameters set forth in Example 1 below. The refractory layer (30)is formed of a plurality of sublayer groups, each sublayer groupcomprising a TiN sublayer (white) and adjacent alumina sublayer (black).As illustrated by the SEM image, the TiN sublayers comprise nodulesinterfacing with the adjacent alumina sublayers. The nodules exhibitvarious regular and irregular morphologies as white specs throughout therefractory layer. FIG. 4 provides an SEM image of a section of therefractory layer detailed in FIG. 3. The SEM image of FIG. 4 was takenat a magnification of 50,000×. TiN nodules are clearly evidenced in FIG.4 and extend across both surfaces of the TiN sublayers, providingresistance to delamination and improving refractory layer properties athigh temperatures, such as those often encountered in cuttingoperations.

Nodules of the Group IVB metal nitride sublayer can be formed during CVDof the nitride sublayer by one or a combination of pathways. In someembodiments, for example, flow of the Group IVB metal reactant gas canbe ramped to precipitate non-uniform growth of the Group IVB metalnitride sublayer leading to nodule formation in the layer. Further, thesudden change in deposition environment from alumina to Group IVB metalnitride, such as TiN, can result in nucleation of larger Group IVB metalnitride grains, thereby providing nodules. Further, Group IVB metalnitride grains can aggregate during deposition forming the nodules. CVDdeposition conditions described further herein can be chosen toeffectuate one or more of these pathways of nodule formation.

As sublayer groups can be formed independent of one another, the GroupIVB metal can be the same or vary among the sublayer groups forming therefractory layer. When varied, the Group IVB metals can present anydesired pattern such as alternating or periodic distribution along thecross-sectional thickness of the refractory layer. Alternatively, theGroup IVB metals can exhibit a random distribution.

The adjacent alumina sublayer of a sublayer group can also be ananolayer, having a thickness less than 0.5 μm. In some embodiments, analumina sublayer has a thickness selected from Table III.

TABLE III Alumina Sublayer Thickness ≤250 nm ≤100 nm  10 nm-200 nm  5nm-100 nm 20 nm-80 nmMoreover, an alumina sublayer of a sublayer group can have an averagegrain size less than 200 nm. In some embodiments, average alumina grainsize ranges from 5 nm to 100 nm or 20 nm to 80 nm. FIG. 5(a) is a planview SEM image of an alumina sublayer, according to one embodiment,illustrating morphology and submicron or nano-size of the aluminagrains. This submicron size and morphology contrast sharply with priorCVD alumina grains provided in the SEM image of FIG. 5(b). Thickness andaverage grain size of the alumina sublayer is controlled by theintervening deposition of the Group IVB metal nitride sublayer. Forexample, such intervening deposition can terminate alumina sublayergrowth and require renucleation of successive alumina sublayer(s).Depending on deposition conditions, an alumina sublayer can beα-alumina, κ-alumina or mixtures (α/κ) thereof. Additionally, in someembodiments, Group IVB metal can be present in the adjacent aluminasublayer, forming doped alumina phases such as TiAl₂O₃ and/or ZrAl₂O₃.As set forth in the CVD parameters described herein, transitioningbetween Group IVB metal nitride sublayer and alumina sublayer can permitintroduction of Group IVB metal dopant into the alumina sublayer. Dopedalumina phases can generally exist at or proximate interfaces with GroupIVB metal nitride sublayers.

The refractory layer comprising the plurality of sublayer groups, insome embodiments, is deposited directly on the substrate surface.Alternatively, a coating described herein can further comprise one ormore inner layers between the refractory layer and the substrate. Innerlayer(s), in some embodiments, comprise one or more metallic elementsselected from the group consisting of aluminum and metallic elements ofGroups IVB, VB and VIB of the Periodic Table and one or morenon-metallic elements selected from Groups IIIA, IVA, VA and VIA of thePeriodic Table. In some embodiments, one or more inner layers betweenthe substrate and refractory layer comprise a carbide, nitride,carbonitride, oxycarbonitride, oxide or boride of one or more metallicelements selected from the group consisting of aluminum and metallicelements of Groups IVB, VB and VIB of the Periodic Table.

For example, one or more inner layers are selected from the groupconsisting of titanium nitride, titanium carbonitride, titaniumoxycarbonitride, titanium carbide, zirconium nitride, zirconiumcarbonitride, hafnium nitride and hafnium carbonitride. Further, a layerof titanium oxycarbonitride can be employed as a bonding layer for therefractory layer and inner layers of the coating. Inner layer(s) of thecoating can have any thickness not inconsistent with the objectives ofthe present invention. In some embodiments, a single inner layer canhave a thickness of at least 5 μm. Alternatively, a plurality of innerlayers can collectively achieve thickness of at least 5 μm. CVD of therefractory layer directly on the substrate or on an inner layer canbegin with an alumina sublayer or Group IVB metal nitride sublayer.

The refractory layer comprising the plurality of sublayer groups can bethe outermost layer of the coating. Alternatively, a coating describedherein can comprise one or more outer layers over the refractory layer.Outer layer(s) can comprise one or more metallic elements selected fromthe group consisting of aluminum and metallic elements of Groups IVB, VBand VIB of the Periodic Table and one or more non-metallic elementsselected from Groups IIIA, IVA, VA and VIA of the Periodic Table. Outerlayer(s) over the refractory layer can comprise a carbide, nitride,carbonitride, oxycarbonitride, oxide or boride of one or more metallicelements selected from the group consisting of aluminum and metallicelements of Groups IVB, VB and VIB of the Periodic Table. For example,one or more outer layers are selected from the group consisting oftitanium nitride, titanium carbonitride, titanium oxycarbonitride,titanium carbide, zirconium nitride, zirconium carbonitride, hafniumnitride, hafnium carbonitride and alumina and mixtures thereof.

Outer layers of coatings described herein can have any thickness notinconsistent with the objectives of the present invention. A coatingouter layer, in some embodiments, can have a thickness ranging from 0.2μm to 5 μm.

Coatings described herein can be subjected to post-coat treatments.Coatings, for example, can be blasted with various wet and/or dryparticle compositions. Post coat blasting can be administered in anydesired manner. In some embodiments, post coat blasting comprises shotblasting or pressure blasting. Pressure blasting can be administered ina variety of forms including compressed air blasting, wet compressed airblasting, pressurized liquid blasting, wet blasting and steam blasting.Wet blasting, for example, is accomplished using a slurry of inorganicand/or ceramic particles, such as alumina, and water. The aluminaparticle slurry can be pneumatically projected at a surface of thecoated cutting tool body to impinge on the surface of the coating. Thealumina particles can generally range in size between about 20 μm andabout 100 μm.

Blasting parameters include pressure, angle of impingement, distance tothe part surface and duration. In some embodiments, angle of impingementcan range from about 10 degrees to about 90 degrees, i.e., the particlesimpinge the coating surface at an angle ranging from about 10 degrees toabout 90 degrees. Suitable pressures can range from 30-55 pounds persquare inch (psi) at a distance to the coated surface of 1-6 inches.Further, duration of the blasting can generally range from 1-10 secondsor longer. Blasting can be generally administered over the surface areaof the coating or can be applied to select locations such as in aworkpiece contact area of the cutting tool. A workpiece contact area canbe a honed region of the cutting tool.

In other embodiments, a coating is subjected to a polishing post-coattreatment. Polishing can be administered with paste of appropriatediamond or ceramic grit size. Grit size of the paste, in someembodiments, ranges from 1 μm to 10 μm. In one embodiment, a 5-10 μmdiamond grit paste is used to polish the coating. Further, grit pastecan be applied to the CVD coating by any apparatus not inconsistent withthe objectives of the present invention, such as brushes. In oneembodiment, for example, a flat brush is used to apply grit paste to theCVD coating in a workpiece contact area of the cutting tool.

A coating described herein can be blasted or polished for a time periodsufficient to achieve a desired surface roughness (R_(a)) and/or otherparameters such as reducing residual tensile stress in the coating. Insome embodiments, a coating subjected to post-coat treatment has asurface roughness (R_(a)) selected from Table IV.

TABLE IV Post-Coat Surface Roughness (R_(a)) Coating Surface Roughness(R_(a)) - nm ≤500 ≤250  <200 10-250 50-175 25-150Coating surface roughness can be determined by optical profilometryusing WYKO® NT-Series Optical Profilers commercially available fromVeeco Instruments, Inc. of Plainview, N.Y.

Further, a post-coat treatment, in some embodiments, does not remove oneor more outer layers of the coating. In some embodiments, for example, apost-coat treatment does not remove an outer layer of TiN, TiCN and/orTiOCN. Alternatively, a post-coat treatment can remove or partiallyremove one or more outer layers, such as TiN, TiCN and TiOCN.

A coating described herein comprising a refractory layer having aplurality of sublayer groups has nanohardness of at least 23 GPa. Insome embodiments, the coating has a nanohardness of 23 GPa to 35 GPa.Coating nanohardness can be in the as-deposited state. Alternatively,the nanohardness can reflect a blasted or polished condition of thecoating. Coating nanohardness values recited herein were determined fromnano-indentation testing conducted with a Fischerscope HM2000 inaccordance with ISO standard 14577 using a Vickers indenter. Indentationdepth was set to 0.2 μm.

As described herein, the refractory layer formed of the sublayer groupsis deposited by CVD. The Group IVB metal nitride sublayer, for example,can be deposited from a gaseous mixture comprising H₂, N₂ and gaseousreactant containing the Group IVB metal. In some embodiments, thegaseous reactant is metal chloride, such as MCl₄, wherein M is a GroupIVB metal.

General CVD processing parameters for a Group IVB metal nitride sublayerhaving a plurality of nodules is provided in Table V.

TABLE V Group IVB Metal Nitride Sublayer CVD Processing Parameters H₂ N₂MCl₄ Temp. Pressure Time Process Step vol. % vol. % vol. % ° C. torrmin. MN* Bal. 12-20 0.2-2 900-1000 40-100 5-30 *M = Group IVB metalAs described above, the Group IVB metal reactant gas can be ramped orotherwise varied within the parameters of Table V to induce formation ofthe nodules. Moreover, the remaining nodule formation pathways and/ormechanisms discussed hereinabove may also contribute during depositionof the Group IVB metal nitride sublayer.

The alumina sublayer adjacent to the Group IVB metal nitride sublayercan be deposited from a gaseous mixture of AlCl₃, H₂, CO₂, HCl andoptionally H₂S. General CVD processing parameters for depositing analumina sublayer are provided in Table VI.

TABLE VI Alumina Sublayer CVD Processing Parameters H₂ AlCl₃ CO₂ CO H₂SHCl Temperature Pressure Time Process Step vol. % vol. % vol. % vol. %vol. % vol. % ° C. torr min. Al₂O₃ Bal. 1-5 0.5-6 — 0.05-0.6 1-5950-1050 30-120 6-200The refractory layer can be deposited directly on the substrate surface.Alternatively, a plurality of coating inner layers can reside betweenthe substrate and refractory layer. General CVD deposition parametersfor various inner layers are provided in Table VII.

TABLE VII CVD Parameters for Inner layer Deposition Base LayerTemperature Pressure Duration Composition Gas Mixture ° C. torr min. TiNH₂, N₂, TiCl₄ 800-900 45-70 10-90  MT-TiCN H₂, N₂, TiCl₄, CH₃CN 750-90050-75 50-400 HT-TiCN H₂, N₂, TiCl₄, CH₄  900-1050  45-120 30-200 TiOCNH₂, N₂, TiCl₄, CH₄,  900-1050 150-400 30-70  COThe foregoing general CVD parameters for inner layer deposition, in someembodiments, can be applied for deposition of one or more outer layersover the refractory layer.

These and other embodiments are further illustrated in the followingnon-limiting examples.

Example 1—Coated Cutting Tools

Coated cutting tools described herein were produced by placing cementedtungsten carbide (WC—Co) cutting insert substrates [ANSI standardgeometry CNMG432RN] into an axial flow hot-wall CVD reactor. The cuttinginserts comprised 6 wt. % cobalt binder with the balance WC grains ofsize 1-5 μm. A coating including a refractory layer comprising aplurality of sublayer groups was deposited on the cutting insertsaccording to Tables VIII and IX. Specifically, the refractory layerswere formed of 64 sublayer groups, each sublayer group comprising a TiNsublayer and an alumina sublayer, wherein the TiN sublayer comprisednodules of TiN interfacing with the alumina sublayer. Each aluminasublayer had a thickness of approximately 40-100 nm, and each TiNsublayer had a thickness of approximately 20-40 nm. The refractory layermorphology was consistent with the cross-sectional SEMs provided inFIGS. 3 and 4 discussed above. Depositions of the alumina sublayers andTiN sublayers were administered in alternating fashion to form therefractory layer. An outer layer of TiN was deposited over therefractory layer to complete the coating.

TABLE VIII CVD Deposition Steps of Coating H₂ N₂ TiCl₄ CH₃CN CH₄ AlCl₃CO₂ CO H₂S HCl Process Step vol. % vol. % vol. % vol. % vol. % vol. %vol. % vol. % vol. % vol. % TiN Bal. 18.40 0.95 — — — — — — — MT-TiCNBal. 27.8  1.31 0.001 — — — — — 1.40 HT-TiCN Bal. 16.69 0.76 — 3.70 — —— — — TiOCN Bal. 17.50 1.08 — 2.52 — — 1.10 — 1.10 Al₂O₃* Bal. — — — —4.84 2.42 — 0.10 3.00 MN* Bal. 18.00 0.95 — — — — — — — TiN Bal. 26.000.80 — — — — — — 0.72 *Alternating Deposition to form sublayer groups

TABLE IX CVD Deposition Steps Temp. Pressure Time Process Step ° C. torrmin. TiN 850-960  45-70 10-90 MT-TiCN 900-940  50-75 50-400 HT-TiCN900-1050  45-120 30-200 TiOCN 950-1050 150-400 30-70  Al₂O₃* 950-1050 30-120  6-200* TiN* 900-1000  40-100  5-30* TiN** 850-960  45-70 10-200*Per sublayer deposition **Outer layer

The resulting multilayer coating exhibited the properties provided inTable X.

TABLE X Properties of CVD Coating Coating Layers Thickness (μm) TiN 0.5MT-TiCN 9.0 HT-TiCN 0.8 [Al₂O₃/TiN]₆₄ 11.2 TiN 1.5

Example 2—Coating Hardness

Coated cutting tools of Example 1 were subjected to nanohardnesstesting. Nanohardness was determined from nano-indentation testingconducted with a Fischerscope HM2000 in accordance with ISO standard14577 using a Vickers indenter. Indentation depth was set to 0.2 μm.Nanohardness was determined for coated cutting tools of Example 1 in theas-deposited state and blasted state. Post-coat blasting wasadministered with an alumina particle slurry for 3-5 seconds with threenozzles. The nozzles provided angles of impingement of 10, 40 and 80degrees. Blasting removed the outermost TiN layer of the coating.Nanohardness was also determined for comparative cutting inserts ofidentical ANSI geometry having a CVD coating detailed in Table XI(Comparative 1).

TABLE XI Comparative Cutting Insert CVD Coating Coating Layers Thickness(μm) TiN 0.4 MT-TiCN 10.2 HT-TiCN 0.9 α-Al₂O₃ 8.4 TiN 1.5Nanohardness was determined for the Comparative cutting inserts in theas-deposited state and blasted state. Blasting conditions for theComparative cutting inserts were the same as that employed for thecutting inserts of Example 1. The results of the nanohardness testingare provided in Table XII.

TABLE XII CVD Coating Nanohardness Cutting Insert Nanohardness (GPa)Example 1 - as deposited 29.5 Comparative 1 - as deposited 26 Example1 - wet blasted 33.5 Comparative 1 - wet blasted 27

Example 3—Metal Cutting Testing

Coated cutting inserts of Example 1 and Comparative cutting inserts (1and 2) were subjected to continuous turning testing according to theparameters below. Comparative 1 exhibited the CVD coating architecturein Table XI above. Comparative 2 employed a cemented carbide substrateconsistent with the Example 1 and Comparative 1 and was provided the CVDcoating detailed in Table XIII.

TABLE XIII CVD Coating of Comparative Insert 2 Coating Layers Thickness(μm) TiN 0.5 MT-TiCN 10.2 HT-TiCN 1.0 [Al₂O₃/TiOCN]₆₄ 10.0 TiN 1.2

As provided in Table XIII, the CVD coating of Comparative 2 included arefractory layer having multilayer architecture. The refractory layer,however, did not include sublayers having nodules as provided by the TiNsublayers of Example 1. For the turning testing, two separate cuttinginserts were tested for each coating architecture of Example 1,Comparative 1 and Comparative 2 to generate repetition 1, repetition 2and mean cutting lifetime.

Turning Parameters

Workpiece: 1045 Steel

Speed: 1100 sfm

Feed Rate: 0.012 ipr

Depth of Cut: 0.08 in

Lead Angle: −5°

End of Life was registered by one or more failure modes of:

Uniform Wear (UW) of 0.012 inches

Max Wear (MW) of 0.012 inches

Nose Wear (NW) of 0.012 inches

Depth of Cut Notch Wear (DOCN) of 0.012 inches

Trailing Edge Wear (TW) of 0.012 inches

The results of the continuous turning testing are provided in Table XIV.

TABLE XIV Continuous Turning Testing Results Coated Repetition 1Repetition 2 Mean Cutting Cutting Insert Lifetime (min.) Lifetime (min.)Lifetime (min.) Example 1 11.9 12.8 12.35 Comparative 1 11.6 11.3 11.45Comparative 2 8.4 7.6 8.0As provided in Table XIV, the coated cutting insert of Example 1 havingan inter-anchored CVD coating architecture described herein outperformedComparative inserts 1 and 2.

Various embodiments of the invention have been described in fulfillmentof the various objects of the invention. It should be recognized thatthese embodiments are merely illustrative of the principles of thepresent invention. Numerous modifications and adaptations thereof willbe readily apparent to those skilled in the art without departing fromthe spirit and scope of the invention.

The invention claimed is:
 1. A coated article comprising: a substrate;and a coating deposited by chemical vapor deposition (CVD) adhered tothe substrate, the coating including a refractory layer comprising aplurality of sublayer groups, a sublayer group comprising a Group IVBmetal nitride sublayer and an adjacent alumina sublayer, the Group IVBmetal nitride sublayer comprising a plurality of Group IVB metal nitridenodules interfacing with the alumina sublayer, wherein Group IVB metaldopant is present in the alumina sublayer.
 2. The coated article ofclaim 1, wherein the sublayer groups are adjacent to one another in therefractory layer.
 3. The coated article of claim 1, wherein sublayergroups are spaced apart from one another by one or more interveningrefractory layers.
 4. The coated article of claim 1 comprising 4 to 100sublayer groups.
 5. The coated article of claim 1, wherein the Group IVBmetal is the same between the Group IVB metal nitride sublayers.
 6. Thecoated article of claim 1, wherein the Group IVB metal varies betweenthe Group IVB metal nitride sublayers.
 7. The coated article of claim 1,wherein the nodules have a size of 20 nm to 500 nm.
 8. The coatedarticle of claim 1, wherein the Group IVB metal dopant forms one or moredoped alumina phases.
 9. The coated article of claim 8, wherein thedoped alumina phase comprises TiAl₂O₃.
 10. The coated article of claim8, wherein the doped alumina phase comprises ZrAl₂O₃.
 11. The coatedarticle of claim 1, wherein the alumina sublayer is a nanolayer.
 12. Thecoated article of claim 11, wherein the alumina sublayer has a thicknessless than 0.5 μm.
 13. The coated article of claim 1, wherein the nodulesare distributed along surfaces of the Group IVB metal nitride sublayer.14. The coated article of claim 2, wherein nodules of a Group IVB metalnitride sublayer interface with alumina sublayers of adjacent sublayergroups.
 15. The coated article of claim 1, wherein the alumina sublayercomprises α-alumina.
 16. The coated article of claim 1, wherein thealumina sublayer has an average grain size less than 100 nm.
 17. Thecoated article of claim 1, wherein the CVD coating has a nanohardness of23 GPa to 35 GPa.
 18. The coated article of claim 1 further comprisingone or more inner layers between the refractory layer and the substrate,an inner layer comprising one or more metallic elements selected fromthe group consisting of aluminum and metallic elements of Groups IVB, VBand VIB of the Periodic Table and one or more non-metallic elements ofGroups IIIA, VI, VA and VIA of the Periodic Table.
 19. The coatedarticle of claim 1, wherein the substrate is cemented carbide, carbide,ceramic, cermet or steel.
 20. The coated article of claim 1, wherein theGroup IVB metal nitride sublayer is titanium nitride.
 21. The coatedarticle of claim 20, wherein the Group IVB metal nitride nodules aretitanium nitride.